'This Week' Transcript: Donald Trump

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ANNOUNCER: Starting right now on ABC's THIS WEEK, GOP showdown -- the candidates facing off in just three days.

For the first time Donald Trump slipping in a key state.

So can Trump take back the spotlight?

The brash billionaire is right here, reviewing his next move.

The comeback -- Hillary Clinton riding high. But with Democrats back on the campaign trail in Iowa...

UNIDENTIFIED MALE: Thank you, Iowa.

ANNOUNCER: -- the new hurdles ahead and her new message at a major event overnight.

HILLARY CLINTON (D), PRESIDENTIAL CANDIDATE: I'm just getting warmed up.

ANNOUNCER: And an American soldier killed during a daring rescue in Iraq. Our troops in Afghanistan staying later than expected -- Martha Raddatz with a rare inside look at the threat to our troops.

From ABC News, THIS WEEK WITH GEORGE STEPHANOPOULOS begins now.

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GEORGE STEPHANOPOULOS, ABC HOST: Good morning.

The presidential campaigns took a tough new turn overnight, with Donald Trump raising questions about Ben Carson's religion, Carson demanding an apology and Donald Trump is standing by live to respond.

And on the Democratic side, Bernie Sanders strikes the sharpest contrast yet with Hillary Clinton, echoing the Iowa speech that launched Barack Obama's campaign eight years ago.

ABC's David Wright was there and he starts us off off from Iowa -- good morning, David.

DAVID WRIGHT, ABC NEWS CORRESPONDENT: Good morning, George.

Bernie Sanders never mentioned her by name, but as he ticked down the issues -- the environment, the Iraq War, same-sex marriage -- he made the case that his views haven't changed with the polls. Sharp elbows there, just as Clinton was beginning to breathe easy.

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WRIGHT (voice-over): Ninety-nine days until the Iowa caucuses and Hillary Clinton is enjoying a comeback. Fans and supporters gathered early, serenaded by pop star Katie Perry, dressed like a patriotic superhero.

Clinton is the woman of the hour, but does she have the nomination locked down?

She got a warm reception last night.

CLINTON: I'm not running for my husband's third term and I'm not running for Barack Obama's third term, I'm running for my first term.

WRIGHT: But don't count her opponent out just yet.

UNIDENTIFIED MALE: Everybody is saying it's all over.

Did you not get the message?

WRIGHT: Vermont Senator Bernie Sanders laughs off that suggestion.

SEN. BERNIE SANDERS (I-VT), DEMOCRATIC PRESIDENTIAL CANDIDATE: I think we are going to prove the pundits wrong again. I believe we're going to make history one more time.

WRIGHT: He's now taking some of his sharpest shots yet at Clinton, calling her out for flip-flopping on the president's new trade deal, for instance. Clinton had called it the gold standard. Now, she's against it.

SANDERS: That agreement is not now nor has it ever been the gold standard of trade agreements. I did not support it yesterday. I do not support it today and I will not support it tomorrow.

WRIGHT: Still, it caps off what may be Clinton's best week since she announced her candidacy. Not only did three potential rivals, including Vice President Biden, veer out of her path, but she managed to hold her own at the Benghazi hearings.

CLINTON: I'm sorry that it doesn't fit your narrative, Congressman. I can only tell you what the facts were.

WRIGHT: Clinton's worst enemy could still be herself. There's still that FBI investigation of her email server and the fact she's a partisan lightning rod.